A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces (a disk may also be referred to as a platter). When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head which is positioned over a specific location of a disk by an actuator.
A read/write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. As a magnetic dipole field decreases rapidly with distance from a magnetic pole, the distance between a read/write head and the surface of a magnetic-recording disk must be tightly controlled. An actuator relies on suspension's force on the read/write head to provide the proper distance between the read/write head and the surface of the magnetic-recording disk while the magnetic-recording disk rotates. A read/write head therefore is said to “fly” over the surface of the magnetic-recording disk. When the magnetic-recording disk stops spinning, a read/write head must either “land” or be pulled away onto a mechanical landing ramp from the disk surface. Because the read/write head flies so close to the surface of the magnetic-recording disk, the components within the HDD may be sensitive to moisture, contaminants, and other impurities and imperfections within the protective enclosure of the HDD.
Over time, the design of new HDD models has enabled lower and lower fly heights. As fly heights decrease, magnetic storage devices (such as HDDs) are at increased risk to experiencing harm from high internal water vapor concentration. High concentrations of water vapor can alter fly heights and thus impact error rates or even wear upon the magnetic-recording head. In addition, high concentration of water vapor can promote various undesirable processes such as corrosion. To illustrate, at 30° C. there is a relatively small change in the fly height if there is an increase in internal humidity; however, at 60° C. (which is a common internal operating temperate of a HDD in a data center), the effect is much more pronounced and typical air bearings of the magnetic read/write head will cause a significant decrease in the fly height as the humidity rises.
Desiccants may be used within electronic equipment (such as a HDD) to reduce concentrations of water vapor therein.